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This page is about the use of tools by non-human animals. For tool use by humans, see Technology and Tools.

Some organisms use tools to perform tasks such as acquiring food and water, grooming, defense, or construction. There is considerable debate over what constitutes a tool, and therefore also which behaviors in nature exemplify tool use. Although the definition of tool use is often vague, it can be defined as the manipulation of an external object to alter the properties of another object or to “mediate the flow of information between the tool user and the environment or other organisms.” Tool use in the animal kingdom is rare, but examples of organisms that use tools include mammals, birds, fish, cephalopods, and insects. In mammals and birds, tool use is associated with larger brain size, social transmission of knowledge, and innovation.

Definitions and terminology

The key to identifying tool use is defining what constitutes a tool. Researchers of animal behavior have arrived at different formulations.

In 1980, Beck published a widely used definition of tool use. More recently, this has been modified as follows:

"The external employment of an unattached or manipulable attached environmental object to alter more efficiently the form, position, or condition of another object, another organism, or the user itself, when the user holds and directly manipulates the tool during or prior to use and is responsible for the proper and effective orientation of the tool."

Other, briefer definitions have been proposed:

"An object carried or maintained for future use."

— Finn, Tregenza, and Norman, 2009.

"The use of physical objects other than the animal's own body or appendages as a means to extend the physical influence realized by the animal."

— Jones and Kamil, 1973

"An object that has been modified to fit a purpose" or "An inanimate object that one uses or modifies in some way to cause a change in the environment, thereby facilitating one's achievement of a target goal."

— Hauser, 2000

Different terms have been given to the tool according to whether the tool is altered by the animal. If the "tool" is not held or manipulated by the animal in any way, such as an immobile anvil, objects in a Bowerbird's bower, or a bird using bread as bait to catch fish, it is sometimes referred to as a "proto-tool."

When an animal uses a tool that acts on another tool, this has been termed use of a "meta-tool." For example, New Caledonian crows will spontaneously use a short tool to obtain an otherwise inaccessible longer tool that then allows them to extract food from a hole. Similarly, bearded capuchin monkeys will use smaller stones to loosen bigger quartz pebbles embedded in conglomerate rock, which they subsequently use as tools.

Rarely, animals may use one tool followed by another, for example, bearded capuchins use stones and sticks, or two stones. This is called "associative," "secondary" or "sequential" tool use.

Borderline examples

Play: Play has been defined as “activity having no immediate benefits and structurally including repetitive or exaggerated actions that may be out of sequence or disordered.” When play is discussed in relation to manipulating objects, it is often used in association with the word "tool." Some birds, notably crows, parrots and birds of prey "play" with objects, many of them playing in flight with such items as stones, sticks, and leaves, by letting them go and catching them again before they reach the ground. A few species repeatedly drop stones, apparently for the enjoyment of the sound effects. Many other species of animals, both avian and non-avian, play with objects in a similar manner.

Fixed "devices": The impaling of prey on thorns by many of the shrikes (Laniidae) is well known. Several other birds may use spines or forked sticks to anchor a carcass while they flay it with the bill. It has been stated that: "this is an example of a fixed device which serves as an extension of the body, in this case, talons," and is thus a true form of tool use. On the other hand, the use of fixed skewers may not be true tool use because the thorn (or whatever) is not manipulated by the bird. Leopards perform a similar behaviour by dragging carcasses up trees and caching them in the forks of branches.

Use of baits: Several species of herons such as the striated heron (Butorides striatus) will place bread in the water to attract fish. Whether this is tool use is disputed because the bread is not manipulated or held by the bird.

Social learning, culture, and cognition

Some forms of tool use appear to be acquired through independent or social learning. For example, in some species such as chimpanzees, orangutans, and bottlenose dolphins, infants learn how to use tools by observing their mothers. Most species that learn to forage with tools are social animals and/or have a period of a close parent-offspring relationship that would facilitate learning from observation. All tool-using birds and primates feed in groups, suggesting that socially facilitated behavior could provide the basis for learned tool use. An individual must possess the cognitive capacity to innovate and the opportunity for social learning in order to learn how to use tools. In fact, it has been theorized that the evolution of intelligence may have been a byproduct of social learning necessary for tool use, which would explain why both tool use and intelligence are most common in social animals. However, social learning is not essential to tool use. For example, the juvenile woodpecker finch develops tool use regardless of whether it has a model to learn from.

Tool use is also cited as an example of culture in chimpanzees, orangutans, bottlenose dolphins, and other organisms. Culture can be defined as a system of socially transmitted behaviors that are demonstrated in most or all individuals in the relevant group at a particular site, but absent in at least one other ecologically similar site. Geographic variation in tool use in chimpanzees and orangutans has been cited as evidence of culture.

Tool use is also associated with a high level of cognitive activity. Several studies in primates and birds have found that tool use is correlated with an enlargement of the brain as a whole or of particular regions. For example, true tool-using birds have relatively larger brains than proto-tool users. Behaviors associated with tool use are linked to networks involving the temporal, parietal, and frontal areas within the left cerebral hemisphere.

Evolution of Tool Use

While no single explanation can account for the appearance of all examples of tool use by animals, it seems probable that many examples could have originated as a result of accidents involving a pre-existing behavior pattern in a new situation. For example, in the face of unattainable food items, animals may have redirected their activities to naturally occurring objects near them. If the resulting activities proved to be rewarding, by allowing the animal access to a food source, the behavior would be reinforced and thus likely repeated.

In the case of Darwin’s finches, if a finch was unable to attain visible insects in a deep crevice of a tree, it may have redirected its attention to gathering twigs for a nest. While carrying a twig, a finch could be re-attracted to the crevice and insert the twig into the space, accidentally dislodging an insect. Thus the finch could learn to associate the twig use with the reward of food and begin to habitually use tools to forage. Other finches may develop the same behavior independently, or learn from observing the original finch. While this theory is speculative, it exemplifies a possible explanation for the development of tool use while foraging in many different environments and situations.

Tool Use is Not Uniquely Human

Although today it is well known that a wide variety of animals exhibit tool use, it was once thought that this was a uniquely human skill. One of the hallmarks of the human species is material culture, or the relationship between material objects and their meaning in a specific culture. Therefore, it is not surprising that researchers once had this impression that humans were the only species to use tools. This common belief was questioned, however, in 1960, when famed field biologist Jane Goodall witnessed chimpanzees manipulating grass and twigs to obtain termites for food. Since the discovery of tool use by chimpanzees, scientists have investigated the evolution of tool use in other primates. Primates continue to be one of the major species studied in regards to tool use by animals. Although hominids (Hominidae), or more recent primate lineages such as chimpanzees and humans, were likely not the first primates to make use of tools since some extant primates also do, the origin of material culture is often studied in Plio-Pleistocene hominids, which are known to have used various tools. One of the key factors in the explosive increase in tool use among hominids was mutual tolerance, or tolerance of the presence of others, as they likely had to share food and process tools to acquire large, sharable meals.

The first manufactured stone tools appear in the archaeological record about 2.5 million years ago, and it is likely that hominid tool use was not as advanced before then. As the use of feeding tools can significantly contribute to fitness in extant pre-agricultural people, many of the tools found in hominid sites are thought to be involved in food processing. Compared to other kinds of tools, feeding tools are more likely to require modification. Most of the great ape tool users learn to make feeding tools through various forms of social learning, comparable to those involved in human material culture. The most likely features that differentiated stone-tool-making hominids from other great apes are increased intelligence or a higher degree of mutual tolerance accompanied by increased opportunities for strong reliance on tools. It is likely that these new tool usage skills would in fact reflect increased cognitive abilities, and such abilities would not be maintained in the population unless accompanied by favorable social conditions for invention and transmission.

In mammals

Primates

Tool use has been reported many times in both wild and captive primates, particularly the great apes. The use of tools by primates is varied and includes hunting (mammals, invertebrates, fish), collecting honey, processing food (nuts, fruits, vegetables and seeds), collecting water, and providing weapons and shelter. In Gombe National Park in 1960, Jane Goodall observed a chimpanzee, David Greybeard, poking pieces of grass into a termite mound and then raising the grass to his mouth. After he left, Goodall approached the mound and repeated the behaviour because she was unsure what David was doing. She found that the termites bit onto the grass. David had been using the grass as a tool to “fish” or "dip" for termites.

Tool manufacture is much more rare than tool use and probably represents higher cognitive functioning. Soon after her initial discovery of David's tool use, Goodall observed other chimpanzees picking up leafy twigs, stripping off the leaves and using the stems to fish for insects. This change of a leafy twig into a tool was a major discovery. In 1990, it was claimed that the only primate to manufacture tools in the wild was the chimpanzee However, since then, several other primates have been reported as tool makers in the wild.

Chimpanzees

Common chimpanzees (Pan troglodytes) are the most sophisticated tool users among all nonhuman primates, as (besides humans) chimpanzees use more tools for more purposes than any other creature. Typical objects chimpanzees turn into tools include stems, twigs, branches, leaves and rocks. They use these objects for many purposes, including feeding, drinking, cleaning themselves, and as weapons. Chimpanzees have even been observed using two tools at once, a stick to dig into an ant nest and a "brush" made from grass stems with their teeth to collect the ants.

• Comparing Chimpanzees and Bonobos

Evolutionarily, the closest living primate relative to the chimpanzee is the bonobo (Pan paniscus). Bonobos use tools as readily as chimpanzees when in captivity, but there are limited reports of bonobos using tools in the wild. It is thought that bonobos lost tool use in the wild because all relevant food sources could be acquired without the help of artifacts. Wild chimpanzees predominantly use tools in the context of food acquisition while wild bonobos appear to use tools mainly for personal care (cleaning, protection from rain) and social purposes.

In captivity, the only major difference in chimpanzee and bonobo tool use is that bonobos of all age-sex classes use tools in a play context, specifically in solitary play, possibly due to their neotenous, or juvenile-like, nature. Bonobos have also been observed in captivity using tools for sexual stimulation , leaves as cover for rain, and branches for social displays . It has been reported that both female chimpanzees and female bonobos not only use tools more avidly than males of their species, but also display a larger range of tool use behaviors. This pattern has not been seen in other great apes, thus suggesting that female-biased tool use evolved prior to the split between bonobos and chimpanzees.

Series of photographs showing a bonobo fishing for termites.

A Bonobo using a stick to "fish" for termites in San Diego Zoo. Stage 1

Stage 2

Stage 3

Extracting the insects

• Ecology and culture

The use of different tools for foraging purposes such as obtaining honey, termites, and ants in distinctive chimpanzee populations can be due to differing ecological conditions, including what food sources and tool sources are abundant in the area. For example, chimpanzees living in Tai National Park crack open nuts with rocks while chimpanzees living in Gombe National Park have not been observed using rocks in this manner However, in some cases tool use cannot be explained by ecological conditions. Extensive surveys of chimpanzee communities have shown that population-specific details of tool use, such as the selection of species of nuts as targets for cracking, cannot be explained purely on the basis of ecological differences. Therefore, chimpanzee tool use is in some sense culturally transmitted. Neighboring chimpanzee communities can come to comprise cultural zones characterized by the possession of certain shared behavioral traditions through immigration, social transmission, and subsequent education through generations. For example, only Tai chimpanzees eat the bone marrow of colobus monkeys with tools. This is evidence of traditional and cultural differences between chimp populations.

Studies have shown that responses of chimpanzees toward novel items in different communities and populations differ with age, as juveniles have been observed as being the most likely to explore tools use with different items. Chimpanzees are also highly specific in their selection of conspecifics as models for observation, as studies have revealed that they mostly observe and imitate activities of individuals in the same age group or older, but not younger than themselves. These results demonstrate a mechanism for the emergence of culture in wild chimpanzees. Tool use emphasizes the role of observational learning both in introducing and maintaining behavioral traditions in wild chimpanzee communities.

• Processing nuts, fruits, vegetables and seeds

A chimpanzee gathering food with a stick

Chimpanzees have been observed opening nuts by pounding with a hammer made of wood or stone. Sometimes, parts of the kernels may be too difficult to be reached with teeth or fingernails, and therefore, some individuals use sticks to remove these remains while others pound the nut further with the hammer. Chimpanzees in the Nimba Mountains of Guinea, Africa use both stone and wooden cleavers as well as stone anvils, to chop up and reduce Treculia fruits into smaller bite-sized portions. These fruits, which can be the size of a volleyball and weigh up to 8.5 kg, are hard and fibrous. Despite lacking a hard outer shell, they are too large for a chimpanzee to wrap its jaws around and bite into. Instead, chimpanzees use a range of tools to chop them into smaller pieces. This is the first account of chimpanzees using a pounding tool technology to break down large food items into bite-sized chunks rather than just extract it from other unobtainable sources such as baobab nuts. Neighbouring chimpanzees in the nearby region of Seringbara do not process their food in this way, again suggesting that tool use among apes is culturally learned.

• Collecting honey

Chimpanzees eat the honey of four bee species. After removing what they can with their hands, groups of chimpanzees fish for the remaining honey in the hives with sticks. They usually use their hands to extract honeycombs from undisturbed hives of honey bees and run away from the bees to eat their catch.

• Collecting water

Both chimpanzees and bonobos have been observed using moss and leaves to make "sponges" that suck up water for grooming. When chimpanzees can't reach water that has formed in hollows inside trees, they have been observed taking a handful of leaves, chewing them, and dipping this “sponge” into the pool to suck out the water.

• Hunting mammals

Chimpanzees sharpen sticks to use as weapons to hunt mammals. This is considered the first evidence of systematic use of weapons in a species other than humans. Researchers documented 22 occasions where wild chimpanzees on a savanna in Senegal fashioned sticks into "spears" to hunt lesser bush babies (Galago senegalensis). In each case, a chimpanzee modified a branch by breaking off one or two ends and, frequently using its teeth, sharpened the stick. The chimpanzee then jabbed the spear into hollows in tree trunks where bush babies sleep. There was a single case in which a chimpanzee successfully extracted a bush baby with the tool.

Chimpanzees regularly eat the marrow of long bones of colobus monkeys with the help of small sticks, after opening the ends of the bones with their teeth. A juvenile female was observed eating small parts of the brain from a skull that she could not break open by inserting a small stick through the foramen magnum. On another occasion, an adult female used three sticks to clean the orbits of a colobus monkey skull after she had just eaten the eyes.

• Hunting invertebrates

Populations differ in the prevalence of tool use for fishing for invertebrates. Chimpanzees in Tai National Park only sometimes use tools, whereas Gombe chimpanzees rely almost exclusively on tools for their intake of driver ants. This may be due to difference in the rewards gained by tool use; Gombe chimpanzees collect 760 ants/min compared to 180 ants/min for the Tai chimpanzees.

Some chimpanzees use tools to hunt large bees (Xylocopa sp.), which make nests in dead branches on the ground or in trees. To get to the grubs and the honey, the chimpanzee first tests for the presence of adults by probing the nest entrance with a stick. If present, adult bees block the entrance with their abdomens, ready to sting. The chimpanzee then disables them with the stick to make them fall out and eats them rapidly. Afterwards, the chimpanzee opens the branch with its teeth to obtain the grubs and the honey.

• Gender and Age

In general, adolescent female and young chimpanzees are seen exhibiting tool use behavior more frequently than adult males. When there is a new innovation, particularly in terms of tool use, the younger generations pick it up very quickly and the last ones to pick it up are adult males. Males stay within their group to spend time with other males.

In wild chimpanzees, the acquisition of tool use behavior in infants appears to be partly socially learned from the mother. During their first year, infant chimpanzees are in constant physical contact with their mothers. Studies have shown that younger chimpanzees learn faster than older chimpanzees when observing tool use in adult chimpanzees for food acquisition.

Recent studies of the Gombe chimpanzees show that young females and males learn to fish for termites differently. Female chimpanzees learn to fish for termites earlier and better than the young males. Females also spend more time fishing while at the mounds with their mothers while males spend more time playing. This behavior may be seen more extensively in females because when they are adults, females need more termite protein, and because with young to care for, they cannot hunt the way males can.

Orangutans

Orangutans (genus Pongo) were first observed using tools in the wild in 1994 in the northwest corner of Sumatra. As with the chimpanzees, orangutans use tools made from branches and leaves to scratch, scrape, wipe, sponge, swat insects, fan, hook, probe, scoop, pry, chisel, hammer, cover, cushion and amplify sound. They will break off a tree branch that is about 30 cm long, snap off the twigs, fray one end and then use the stick to dig in tree holes for termites. Sumatran orangutans use a variety of tools - up to 54 types for extracting insects or honey- and as many as 20 types for opening or preparing fruits such as the hard to access Neesia malayana. They also use an 'autoerotic tool' - a stick which they use to stimulate the genitals and masturbate (both male and female). In parts of Borneo, orangutans use handfuls of leaves as napkins to wipe their chins while orangutans in parts of Sumatra use leaves as gloves, helping them handle spiny fruits and branches, or as seat cushions in spiny trees. It has been reported that a Sumatran orangutan used a large leaf as an umbrella in a tropical rainstorm. There have been reports that individuals in both captivity and in the wild use tools held between the lips or teeth, rather than in the hands. In captivity, orangutans have been taught to chip stone handaxes.

Orangutans produce an alarm call known as a “kiss squeak” when they encounter a predator like a snake or a human. Sometimes, orangutans will strip leaves from a branch and hold them in front of their mouth when making the sound. It has been found this lowers the maximum frequency of the sound i.e. makes it deeper, and in addition, smaller orangutans are more likely to use the leaves.

• Hunting fish

Orangutans living in Borneo scavenge fish that wash up along the shore and scoop catfish out of small ponds for fresh meals. Over two years, anthropologist Anne Russon saw several animals on these forested islands learn on their own to jab at catfish with sticks, so that the panicked prey would flop out of ponds and into the orangutan's waiting hands. Although orangutans usually fished alone, Russon observed pairs of apes catching catfish on a few occasions. On the island of Kaja in Borneo, a male orangutan was observed using a pole apparently trying to spear or bludgeon fish. This individual had seen humans fishing with spears. Although not successful, he was later able to improvise by using the pole to catch fish already trapped in the locals' fishing lines.

• Collecting honey

Sumatran orangutans use sticks to poke a bees' nest wall, move it around and obtain the honey.

• Processing nuts, fruits, vegetables and seeds

Sumatran orangutans use sticks to acquire seeds from a particular fruit. When the fruit of the Neesia tree ripens, its hard, ridged husk softens until it falls open. Inside are seeds that are highly desirable to the orangutans, but they are surrounded by fibreglass-like hairs that are painful if eaten. A Neesia-eating orangutan will select a 12 cm stick, strip off the bark, and then carefully scrape the hairs off with it. Once the fruit is safe, the ape will eat the seeds using the stick or its fingers.

Gorillas

There are few reports of gorillas using tools in the wild.

A gorilla pushing a stick into the ground and using it as a stabilizing stick while dredging aquatic herbs

Western lowland gorillas have been observed using sticks to apparently measure the depth of water and as "walking sticks" to support their posture when crossing deeper water. Another adult female used a detached trunk from a small shrub as a stabilizer during food gathering. Physical differences among the great apes may explain the absence of observed tool use in wild gorillas, as gorillas exploit food resources differently from chimpanzees. While chimpanzee and orangutan feeding involves tools such as hammers to crack open nuts and sticks to fish for termites, gorillas access these foods by breaking nuts with their teeth and smashing termite mounds with their hands.

Capuchin monkeys

The black-striped capuchin (Sapajus libidinosus) was the first non-ape primate for which tool use was documented in the wild; individuals were observed cracking nuts by placing them on a stone anvil and hitting them with another large stone (hammer). Similar hammer-and-anvil use has been observed in other wild capuchins including other robust capuchin monkeys (genus "Sapajus") It may take a capuchin up to 8 years to master this skill. The monkeys often transport hard fruits, stones, nuts and even oysters to an anvil for this purpose.

Capuchins also use stones as digging tools for probing the substrate and sometimes for excavating tubers. Wild black-striped capuchin use sticks to flush prey from inside rock crevices.

Robust capuchins are also known at times to rub defensive secretions from arthropods over their bodies before eating them; such secretions are believed to act as natural insecticides.

In a captive environment, capuchins will readily insert a stick into a tube containing viscous food that clings to the stick, which they then extract and lick. Capuchins also use a stick to push food from the center of a tube retrieving the food when it reaches the far end, and as a rake to sweep objects or food toward themselves.

Baboons

Tool use by baboons in the wild was mentioned by Charles Darwin in his book The Descent of Man, and Selection in Relation to Sex.

Brehm states, on the authority of the well-known traveller Schimper, that in Abyssinia when the baboons belonging to one species (C. gelada) descend in troops from the mountains to plunder the fields, they sometimes encounter troops of another species (C. hamadryas), and then a fight ensues. The Geladas roll down great stones, which the Hamadryas try to avoid...

Darwin continued:

Brehm, when accompanying the Duke of Coburg-Gotha, aided in an attack with fire-arms on a troop of baboons in the pass of Mensa in Abyssinia. The baboons in return rolled so many stones down the mountain, some as large as a man's head, that the attackers had to beat a hasty retreat; and the pass was actually for a time closed against the caravan.

These rather anecdotal reports of stone throwing by baboons have been corroborated by more recent research on chacma baboon (Papio ursinus) troops living on the desert floor of the Kuiseb Canyon in South West Africa. Stoning by these baboons is done from the rocky walls of the canyon where they sleep and retreat when they are threatened. Stones are lifted with one hand and dropped over the side. The stones tumble down the side of the cliff or falls directly to the canyon floor. The researchers recorded 23 such incidents involving the voluntary release of 124 stones, although the purpose of such incidences is not well understood.

A subadult male from a captive group of Guinea baboons (Papio papio) learned, by trial-and-error, to use a tool to rake in food. He then used the tool 104 times over 26 days, thereby providing the group with most of its food.

Mandrills

In the wild mandrills have been observed to clean their ears with modified tools. Scientists filmed a large male mandrill at Chester Zoo (UK) stripping down a twig, apparently to make it narrower, and then using the modified stick to scrape dirt from underneath its toenails.

Macaques

In Thailand and Myanmar, crab-eating macaques use stone tools to open nuts, oysters and other bivalves, and various types of sea snails (nerites, muricids, trochids, etc.) along the Andaman sea coast and offshore islands.

A troop of wild macaques which regularly interact with humans have learnt to remove hairs from the human's heads, and use the hair to floss their teeth.

Elephants

In regards to elephant physiology, the elephant brain seems very well suited to use and manipulate tools, based on similar studies on brain areas involved in tool use in humans. In fact, elephants have been cited as having the highest frequency and diversity of tool use of any non-primate species . Both African elephants (Loxodonta africana) and Asian elephants (Elephas maximus) possess a cerebellum that comprises approximately 18.6% of their brain, which is proportionately 1.8 times larger than in humans. This is mostly attributed to coordinated trunk movements that could aid in tool use, as the cerebellum has also been associated with tool use in human studies in regards to the fine manipulation needed to use tools. Elephants have well-developed frontal and parietal lobes, which are the areas of the brain most associated with specific reasoning and spatial reasoning, respectively . Also, elephants have a disproportionately large temporal lobe. This is mostly linked to the great memory of elephants, but also plays a role in tool use and manipulation in studies with humans . These features of the elephant’s brain physiology, combined with the prehensile trunk, make these animals particularly well-adapted for tool use.

Elephants live in highly social groups, which provides them with opportunities for social learning of behaviors such as tool use.

Elephants show an ability to manufacture and use tools with their trunk and feet. This tool use is most associated with body care, specifically in the removal of ectoparasites and in thermoregulation. Both wild and captive Asian elephants use branches to swat flies or scratch themselves. Eight of 13 captive Asian elephants, maintained under a naturalistic environment, modified branches and swatted with the altered branch, indicating this species is capable of the more rare behaviour of tool manufacture. There were different styles of modification of the branches, the most common of which was holding the main stem with the front foot and pulling off a side branch or distal end with the trunk. Elephants have also been observed digging holes to drink water, then ripping bark from a tree, chewing it into the shape of a ball thereby manufacturing a "plug" to fill in the hole, and covering it with sand to avoid evaporation. They would later go back to the spot to drink.

Asian elephants may use tools in problem solving. A captive male was observed moving a box to a position where it could be stood upon to reach food that had been deliberately hung out of reach. Also, elephants show plasticity in their tool-using behavior. While grazing on grass, an elephant will often pluck the clump of grass from the ground and strike the grass against its leg to remove excess dirt. If the elephant notices water nearby, however, it will use the pond to wash off the dirt instead. This adaptable response is illustrative of an intellectual process occurring in the elephant's brain. Elephants have also been observed dropping large rocks onto an electric fence to either ruin the fence or cut off the electricity.

Social learning is thought to be a key component of tool use in elephants. Young elephants have an extensive developmental dependency on adults, and thus the opportunity for social learning is massive. In a study done by Hart et al., elephants that were 9 and 18 months old showed different levels of tool use aptitude. The 18-month-old elephant removed a side branch and was coordinated in using the branch to swat flies in comparison to the uncoordinated response of the 9-month-old. This difference in aptitude is thought to reflect the difference in the amount of time these young have had to learn .

In regards to the evolutionary significance of tool use in elephants, it is suggested that the tool use may compensate for a ‘lack of biological equipment.’ Large body size and small surface area are good adaptive traits for aquatic animals in retaining heat (a recent ancestor of the elephant was likely a semi-aquatic animal like the hippopotamus), but this body types makes the elephant vulnerable to overheating on land. Elephants also have little protection from flies and other skin irritants due to a lack of fur. These problems may have led to the development of behaviors for overall body care such as cooling, fly swatting, and scratching that all involve tool use. Biting by flies can incur fitness losses to the elephant in the form of loss of blood and the possible introduction of diseases. Therefore, tool use to prevent these fitness losses could have been favored by natural selection. Furthermore, the elephants' feeding niche may have predisposed these animals to tool-using behavior. Most of an elephant’s food, like long grasses, branches, and even whole trees, are potential tools. Interestingly, Hart et al. report that all elephants that were observed fly swatting with branches were foraging at the time.

Bears

Moulting brown bears (Ursus arctos) in Alaska have been observed using rocks to exfoliate.

In a current study at Washington State University, researchers have demonstrated that grizzly bears (Ursus arctos horribilis) can manipulate objects in their environment to reach a food reward that is inaccessible otherwise. The experiment is conducted in two phases; the first phase involves observing whether a bear will use a properly positioned sawed-off tree stump to reach the food reward. Once the bear has been successful in the first portion of the experiment, the tree stump is then moved away from the hanging food reward and placed on its side. The bear must then move the stump into position with the proper orientation to gain access to the food, in order to show that it can manipulate inanimate objects in several steps to achieve a goal. While it is still too early on in the study to reach scientific conclusions, several of the bears have proven to be adept at manipulating the tree stump to gain access to the food.

Cetaceans

Researchers pushed a pole with a conical sponge attached along the substrate to simulate sponging behavior by dolphins. They videotaped this experiment to learn what prey was available on the seafloor and why a sponge would be beneficial to foraging rather than echolocation.

A community of Indo-Pacific bottlenose dolphins (Tursiops aduncus) in Shark Bay, Western Australia, made up of approximately 41-54 animals, are known to use conical sponges (Echinodictyum mesenterinum) as tools while foraging. This behavior, termed “sponging,” occurs when a dolphin breaks off a sponge and wears it over its rostrum while foraging on the seafloor. Sponging behavior typically begins in the second year of life. During sponging, dolphins mainly target fish that lack swimbladders and burrow in the substrate. Therefore, the sponge may be used to protect their rostrums as they forage in a niche where echolocation and vision are less effective hunting techniques. Dolphins tend to carry the same sponge for multiple surfacings but sometimes change sponges. Spongers typically are more solitary, take deeper dives, and spend more time foraging than non-spongers. Despite these costs, spongers have similar calving success to non-spongers.

There is evidence that both ecological and cultural factors predict which dolphins use sponges as tools. Sponging occurs more frequently in areas with higher distribution of sponges, which tends to occur in deeper water channels. Sponging is heavily sex-biased to females . Genetic analyses suggest that all spongers are descendants of a single matriline, suggesting cultural transmission of the use of sponges as tools. Sponging may be socially learned from mother to offspring. Social grouping behavior suggests homophily (the tendency to associate with similar others) among dolphins that share socially learned skills such as sponge tool use. Sponging has only been observed in Shark Bay.

Indo-Pacific bottlenose dolphins in Shark Bay have also been observed carrying conch shells. In this behavior, dolphins insert their rostrum into the shell’s aperture. Although this behavior is rare, it appears to be used for foraging. Dolphins appear to use the conch shells to scoop fish from the substrate then carry the shell to retrieve the fish near the surface.

Sea otters

A sea otter using a rock to break open a shell.

Under each foreleg, the sea otter (Enhydra lutris) has a loose pouch of skin that extends across the chest. In this pouch (preferentially the left one), the animal stores collected food to bring to the surface. This pouch also holds a rock, unique to the otter, that is used to break open shellfish and clams. To open hard shells, it may pound its prey with both paws against the rock, which it places on its chest. Furthermore, sea otters will use large stones to pry an abalone off its rock; they will hammer the abalone shell with observed rates of 45 blows in 15 seconds or 180 rpm. Releasing an abalone, which can cling to rock with a force equal to 4,000 times its own body weight, requires multiple dives by the otter.

Mongooses

Wild banded mongooses (Mungos mungo) regularly use anvils to open prey with a hard shell such as rhinoceros beetles, bird eggs, snail shells or pupating dung beetles. They use a range of anvils commonly including rocks and the stems of trees, but will also use the side-walls of gullys and even dried elephant dung. Pups as young as 2 months of age are already showing the behavioural patterns associated with using an anvil, however, successful smashing is usually shown in individuals older than 6 months of age.

American badgers

North American badgers (Taxidea taxus) hunt Richardson's ground squirrels (Spermophilus richardsonii). The most common hunting technique is excavation of burrow systems, but plugging of openings into ground-squirrel tunnels accounts for 5–23% of hunting actions. Badgers usually use soil from around the tunnel opening, or soil dragged 30–270 cm from a nearby mound to plug tunnels. The least common (6%), but most novel, form of plugging used by 1 badger involved movement of 37 objects from distances of 20–105 cm to plug openings into 23 ground-squirrel tunnels on 14 nights.

In birds

Tool use is found in at least thirty-three different families of birds.

Bird nests show a great diversity in complexity

Relatively simple nest of a Greater Black-backed Gull

Emperor Penguins do not build a nest

Many birds (and other animals) build nests. It can be argued that this behaviour constitutes tool use according to the definitions given above; the birds "carry objects (twigs, leaves) for future use", the shape of the formed nest prevents the eggs rolling away and thereby "extends the physical influence realized by the animal", and the twigs are bent and twisted to shape the nest, i.e. "modified to fit a purpose". The complexity of bird nests varies markedly, perhaps indicating a range in the sophistication of tool use. For example, compare the highly complex structures of weaver birds to the simple mats of herbaceous matter with a central cup constructed by gulls. It is noteworthy that some birds, such as the emperor penguin, do not build nests. The classification of nests as tools has been disputed on the basis that the completed nest, or burrow, is not held or manipulated.

Woodpecker Finches

Perhaps the best known and most studied example of an avian tool user is the woodpecker finch (Camarhynchus pallidus) from the Galápagos Islands. If the bird uncovers prey in bark which is inaccessible, the bird then flies off to fetch a cactus spine which it may use in one of three different ways: as a goad to drive out an active insect (without necessarily touching it); as a spear with which to impale a slow-moving larva or similar animal; or as an implement with which to push, bring towards, nudge an inactive insect from a crevice or hole. Tools that are not exactly fitting the purpose are worked by the bird and adapted for the function thus making the finch a "tool maker" as well as a "tool user". Some individuals have been observed to use a different type of tool with novel functional features - barbed twigs from blackberry bushes, a plant that is not native to the islands. The twigs were first modified by removing side twigs and leaves and then used such that the barbs helped drag prey out of tree crevices.

There is a genetic predisposition for tool use in this species, which is then refined by individual trial-and-error learning during a sensitive phase early in development. This means that, rather than following a stereotypical behavioural pattern, tool use can be modified and adapted by learning.

The importance of tool use by woodpecker finches species differs between vegetation zones. In the arid zone, where food is limited and hard to access, tool use is essential, especially during the dry season. Up to half of the finches' prey is acquired with the help of tools, making them even more routine tool users than chimpanzees. The tools allow them to extract large, nutritious insect larvae from tree holes, making tool use more profitable than other foraging techniques. In contrast, in the humid zone, woodpecker finches rarely use tools, since food availability is high and prey is more easily obtainable. Here, the time and energy costs of tool use would be too high.

Corvids

A New Caledonian crow showing sequential tool use in the laboratory

Corvids are a family of birds characterised by relatively large brains, remarkable behavioural plasticity (especially highly innovative foraging behaviour) and well-developed cognitive abilities.

In the wild

An American crow (Corvus brachyrhynchos) has been observed to modify and use a piece of wood as a probe. Green jays (Cyanocorax yncas) have been observed using sticks as tools to extract insects from tree bark, a behavior which has also been observed and filmed in New Caledonian crows (Corvus moneduloides)[5] The birds poke the insects or larvae until they bite the stick in defence and can be drawn out. This "larva fishing" is very similar to the "termite fishing" practised by chimpanzees. In the wild, stick tools are made from twigs, grass stems or similar plant structures whereas captive individuals have been observed to use a variety of materials, including feathers and garden wire. Stick tools can either be non-hooked - being more or less straight and requiring only little modification - or hooked. Construction of the more complex hooked tools typically involves choosing a forked twig from which parts are removed and the remaining end is sculpted and sharpened. New Caledonian crows also use tools made from barbed leaf edges of screw pines (Pandanus spp.) by precise ripping and cutting, although the function of these tools is not understood.

Crows in urban Japan have been filmed [6] using an innovative technique to crack hard-shelled nuts by dropping them onto cross walks (pedestrian crossings) and letting them be run over and cracked by cars. They then retrieve the cracked nuts when the cars are stopped at the red light. In some towns in America, crows drop walnuts onto busy streets so that the cars will crack the nuts.

Hooded crows (Corvus cornix) use bait to catch fish. Individuals (who may have observed fish being fed bread by humans) will place the bread in the water to attract fish.

In captivity

While young birds in the wild normally learn to make stick tools from elders, a laboratory New Caledonian crow named "Betty" was filmed [7] spontaneously improvising a hooked tool from a wire. It was known that this individual had no prior experience as she had been hand-reared. New Caledonian crows have been observed to use an easily available small tool to get a less easily available longer tool, and then use this to get an otherwise inaccessible longer tool to get food that was out of reach of the shorter tools. One bird, "Sam", spent 110 seconds inspecting the apparatus before completing each of the steps without any mistakes. This is an example of sequential tool use, which represents a higher cognitive function compared to many other forms of tool use. Captive New Caledonian crows have used stick tools to make first contact with objects that were novel and hence potentially dangerous, while other individuals have been observed using a tool when food was within reach but placed next to a model snake. It has been claimed "Their [New Caledonian crow] tool-making skills exceed those of chimpanzees and are more similar to human tool manufacture than those of any other animal."

Other species, such as rooks (Corvus frugilegus), can also make and use tools in the laboratory, showing a degree of sophistication similar to that of New Caledonian crows.

While not confirmed to have used tools in the wild, captive blue jays (Cyanocitta cristata) have been observed using strips of newspaper as tools to obtain food.

Warblers

A pouch constructed by a Tailorbird which contains the nest

The tailorbird (genus Orthotomus) takes a large growing leaf (or two or more small ones) and with its sharp bill pierces holes into opposite edges. It then grasps spider silk, silk from cocoons, or plant fibres with its bill, pulls this "thread" through the two holes, and knots it to prevent it from pulling through (although the use of knots is disputed). This process is repeated several times until the leaf or leaves forms a pouch or cup in which the bird then builds its nest. The leaves are sewn together in such a way that the upper surfaces are outwards making the structure difficult to see. The punctures made on the edge of the leaves are minute and do not cause browning of the leaves, further aiding camouflage. The processes used by the tailorbird have been classified as sewing, rivetting, lacing and matting. Once the stitch is made, the fibres fluff out on the outside and in effect they are more like rivets. Sometimes the fibres from one rivet are extended into an adjoining puncture and appear more like sewing. There are many variations in the nest and some may altogether lack the cradle of leaves.It is believed that only the female performs this sewing behaviour.

Some birds of the genus Prinia also practice this sewing and stitching behaviour.

Parrots

Kea, a highly inquisitive New Zealand mountain parrot, has been filmed stripping twigs and inserting them into gaps in box-like stoat traps to trigger them. Apparently, the Kea's only reward is the banging sound of the trap being set off.

In a similarly rare example of tool preparation, a captive Tanimbar corella (Cacatua goffiniana) was observed breaking off and "shaping" splinters of wood and small sticks to create rakes that were then used to retrieve otherwise unavailable food items on the other side of the aviary mesh. This behaviour has been filmed.[8]

Many owners of household parrots have observed their pets using various tools to scratch various parts of their bodies. These tools include discarded feathers, bottle caps, popsicle sticks, matchsticks, cigarette packets and nuts in their shells.

Hyacinth macaws (Anodorhynchus hyacinthinus) have been repeatedly observed to use tools when breaking open nuts. For example, pieces of wood are used as wedges. Several birds have wrapped a piece of leaf around a nut to hold it in place. This behaviour is also shown by palm cockatoos (Probosciger aterrimus). It seems that the Hyacinth macaw has an innate tendency to use tools during manipulation of nuts, as naïve juveniles tried out a variety of objects in combination with nuts.

Egyptian Vultures

When an Egyptian vulture (Neophron percnopterus) encounters a large egg, it takes a stone into its beak and forcefully throws it at the egg until the shell is broken, usually taking a few minutes. This behaviour, first reported in 1966, seems to be largely innate and is displayed by naïve individuals. Its origin could be related to the throwing of eggs and, interestingly, rounded (egg-like) stones are preferred to jagged ones.

In a small population in Bulgaria, Egyptian vultures use twigs to collect sheep wool for padding their nests. Although both twigs and wool can serve as nesting material, this appears to be deliberate tool use. The birds approached bits of discarded wool with a twig in their beak, which was then either used as a rake, to gather the wool into heaps, or to roll up the wool. Interestingly, wool was collected only after shearing or simulated shearing of sheep had taken place, but not after wool had simply been deposited in sheep enclosures.

Brown-headed Nuthatches

Brown-headed nuthatches (Sitta pusilla) have been observed to methodically use bark pieces to remove other flakes of bark from a tree. The birds insert the bark piece underneath an attached bark scale, using it like a wedge and lever, to expose hiding insects. Occasionally, they reuse the same piece of bark several times and sometimes even fly short distances carrying the bark flake in their beak. The evolutionary origin of this tool use might be related to these birds frequently wedging seeds into cracks in the bark to hammer them open with their beak, which can lead to bark coming off.

Brown-headed nuthatches have also used a bark flake for concealing a seed cache.

Owls

Burrowing Owls (Athene cunicularia) frequently collect mammalian dung, which they use as a bait to attract dung beetles, a major item of prey.

In reptiles

A mugger crocodile in its marshy habitat, where it may use sticks floating on top of the water to lure birds as prey.

Tool use by American alligators (Alligator mississippiensis) and Mugger crocodiles (Crocodylus palustris) has been documented. During breeding season, birds such as herons and egrets look for sticks to build their nests, and in some cases when there is a shortage of sticks in marshy areas where bird and reptile habitats overlap, the search can become extremely competitive. It can sometimes result in birds frantically searching and stealing sticks from other nests. In response, reptiles exploit this desperation, collecting and using these sticks as bait to catch birds. Researchers have observed reptiles lying still in the water with sticks balanced on either their heads or in their mouths, and when a bird approaches, the reptiles spring their trap. This strategy is the first known case of a predator not only using an object as a lure, but also taking into account the seasonal behavior of its prey.

In cephalopods

A small octopus (4-5 cm diameter) individual using a nut shell and clam shell as shelter

At least four veined octopus (Amphioctopus marginatus) individuals were witnessed retrieving coconut shells, manipulating them, stacking them, transporting them some distance (up to 20 metres), and then reassembling them to use as a shelter. The octopuses use coconut shells that have settled in the ocean. They probe their arms down to loosen the mud, then rotate the shells out. After turning the shells so the open side faces upwards, the octopuses blow jets of mud out of the bowl before extending their arms around the shell - or if they have two halves, stacking them first, one inside the other. They then stiffen their legs and move away in a manner which has been called "stilt-walking." The octopuses eventually use the shells as a protective shelter in areas where little other shelter exists. If they just have one half, they simply turn it over and hide underneath. But if they are lucky enough to have retrieved two halves, they assemble them back into the original closed coconut form and sneak inside. This behaviour has been filmed.[9] The authors of the research article claimed this behaviour falls under the definition of tool use because the shells are carried for later use. However, this argument remains contested by a number of other biologists who state that the shells actually provide continuous protection from abundant bottom-dwelling predators in their home range.

Octopuses also deliberately place stones, shells and even bits of broken bottle to form a wall that constricts the aperture to the den. In laboratory studies, Octopus mercatoris, a small pygmy species of octopus, has been observed to block its lair using a plastic Lego block.

In fish

Several species of wrasses have been observed using rocks as anvils to crack bivalve (scallops, urchins and clams) shells. It was first filmed [10] in an orange-dotted tuskfish (Choerodon anchorago) in 2009 by Giacomo Bernardi. The fish fans sand to unearth the bivalve, takes it into its mouth, swims several metres to a rock which it uses as an anvil by smashing the mollusc apart with sideward thrashes of the head. This behaviour has been recorded in a blackspot tuskfish (Choerodon schoenleinii) on Australia's Great Barrier Reef, yellowhead wrasse (Halichoeres garnoti) in Florida and a six-bar wrasse (Thalassoma hardwicke) in an aquarium setting. These species are at opposite ends of the phylogenetic tree in this family, so this behavior may be an ancestral trait in wrasses.

Prior to laying their eggs on a vertical rock face, male and female whitetail major damselfish clean the site by sand-blasting it. The fish pick up sand in their mouths and spit it against the rock face. Then they fan the area with their fins. Finally they remove the sand grains that remain stuck to the rock face by picking them off with their mouths.

Archerfish are found in the tropical mangrove swamps of India and Australasia. They approach the surface, take aim at insects that sit on plants above the surface, squirt a jet of water at them, and grab them after the insects have been knocked off into the water. The jet of water is formed by the action of the tongue, which presses against a groove in the roof of the mouth. Some archerfish can hit insects up to 1.5 m above the water surface. They use more water, which gives more force to the impact, when aiming at larger prey. Triggerfish (Pseudobalistes fuscus) blow water to turn sea urchins over and expose their more vulnerable ventral side.. Whether these later examples can be classified as tool use depends on which definition is being followed because there is no intermediate or manipulated object, however, they are examples of highly specialized natural adaptations.

In insects

Some insect species are also known to use tools. The ant species Conomyrma bicolor have been observed to practice “stone-dropping” behavior, in which stones are picked up with the mandibles and dropped in front of nest entrances of other desert ant species. This has been proposed as a form of interference competition because it keeps other species from foraging. In the subfamily Sphecinae of digger wasps, tools are used for nest closure. After preparing their burrows, the wasp Ammophila picks up a pebble in the mandibles and uses it to compact the soil around the nest. Myrmicinae ants use pieces of leaf, mud and sand as platters to carry soft food and water to the colony. The use of these tools improves the efficiency with which the food is brought back to the colony. The ant species Aphaenogaster rudis conducts a debris dropping behavior during foraging, which may be considered tool use. There is evidence that it may be performed by a specialized subset of foragers in a colony in order to protect other workers from entanglement or drowning in liquids.

See also

• Animal cognition
• Cephalopod intelligence
• Bird intelligence
• Cetacean intelligence
• Elephant intelligence
• Structures built by animals

Further reading

• Robert W. Shumaker; Kristina R. Walkup; Benjamin B. Beck (2011). Animal Tool Behavior: The Use and Manufacture of Tools by Animals. The Johns Hopkins University Press.

External links

• Chimpanzee making and using a termite "fishing rod"
• Chimpanzee using tool to break into beehive to get honey
• Crow making a tool by bending wire to snag food
• Various tool use by birds
• Fish using an anvil to break open prey
• Dolphin using a marine sponge to protect its rostrum
• Mandrill using a tool to clean under its nails

Category:Animal intelligence Category:Ethology